Michael Türkay Memorial Issue
DESCRIPTION OF A NEW SPECIES OF PACHYCHELES (DECAPODA, ANOMURA, PORCELLANIDAE)
FROM THE SOUTHERN CARIBBEAN SEA
BY
BERND WERDING1)and ALEXANDRA HILLER2,3)
1)Institut für Tierökologie und Spezielle Zoologie der Justus-Liebig-Universität Giessen, Heinrich-Buff-Ring 29 (Tierhaus), D-35392 Giessen, Germany
2)Smithsonian Tropical Research Institute, Apartado 0843-03092, Panama, Republic of Panama
ABSTRACT
A new species of porcellanid crab from the southern Caribbean Sea is described. Pachycheles tuerkayi n. sp. has been confused with P. serratus (Benedict, 1901) since the 1950s because the two species are morphologically and ecologically similar and have overlapping distributions in the southern Caribbean. P. tuerkayi n. sp. is restricted to the coasts of Costa Rica, Panamá and Colombia.
P. serratus ranges from Puerto Rico and the Virgin Islands to the coasts of Panamá, Colombia and Venezuela. Genetic differences based on DNA sequences of the mitochondrial 16S rDNA gene from the two species surpassed those estimated for geminate porcellanids on each side of the Isthmus of Panamá. Field observations where P. tuerkayi n. sp. and P. serratus overlap indicated that the two species come into contact when sharing the same substrate. The total number of porcellanid species in the western Atlantic rises to 50.
ZUSAMMENFASSUNG
Eine neue Porzellaniden-Art aus dem Karibischen Meer wird beschrieben. Pachycheles tuerkayi n. sp. und P. serratus (Benedict, 1901), deren Verbreitung sich in der südlichen Karibik überschnei- det, sind, seit den 1950er Jahren, wegen ihrer morphologischen Ähnlichkeiten und wegen ihres Vorkommens in der gleichen ökologischen Situation für eine Art gehalten worden. Die Verbre- itung von P. tuerkayi n. sp. ist auf die Küste von Costa Rica, Panamá und Kolumbien beschränkt, während P. serratus in Puerto Rico, den Jungferninseln, sowie in Panamá, Kolumbien und Venezuela vorkommt. Die genetischen Distanzen, die sich aus dem Vergleich von DNS Sequenzen des mi- tochondrialen 16S rDNS Gens der beiden Arten ergeben, gehen über diejenigen hinaus, die für Zwillingsarten beiderseits des Isthmus von Panamá ermittelt wurden. Feldbeobachtungen im Über- lappungsgebiet beider Arten zeigen, dass diese miteinander in Kontakt kommen können, wenn sie das gleiche Substrat bewohnen. Die Gesamtzahl der west atlantischen Porzellaniden beträgt nun 50 Arten.
3)Corresponding author; e-mail: [email protected]
© Koninklijke Brill NV, Leiden, 2017 DOI 10.1163/15685403-00003684
INTRODUCTION
The porcellanid fauna of the western Atlantic has been intensively studied since the 1950s (Haig, 1956; Gore, 1970, 1982; Gore & Abele, 1976; Werding, 1977, 1978, 1982; Werding & Hiller, 2002). Werding et al. (2003) reported 48 species (including 2 formerly known only from the East Pacific), and Werding & Hiller (2005) added Petrolisthes hispaniolensis Werding & Hiller, 2005, increasing the number to 49 West Atlantic species.
The new species described here as Pachycheles tuerkayi n. sp. was first dis- cerned by Haig (1956) as a pubescent form of the tropical Pachycheles serratus (Benedict, 1901). Haig highlighted a “thick pile of fine hairs” on the chelipeds of specimens from Bahía Caledonia, Panamá. Later, Gore (1970, 1982) recorded the pubescent and non-pubescent forms from Panamá, although Gore & Abele (1976) only referred to pubescent specimens from the same region. Werding (1977) re- ported on the two forms in the area of Santa Marta, Colombia, but only on the pubescent form in the Colombian Gulf of Urabá (Werding, 1978) and Islas del Rosario (Werding, 1982).
Here, we describe the pubescent form as Pachycheles tuerkayi n. sp. and designate the non-pubescent form as P. serratus (fig. 1), as this corresponds to Benedict’s (1901) description (see Discussion). Genetic distances based on DNA sequences of the mitochondrial 16S rDNA gene from the two species were estimated to explore species boundaries and to establish intra- and interspecific divergence. The new species becomes the 50th member of the West Atlantic porcellanid fauna.
MATERIAL AND METHODS
Preserved specimens of Pachycheles serratus and P. tuerkayi n. sp. collected in Panamá (Bocas del Toro, Playa Diablo), Colombia (Islas del Rosario and Santa Marta) and Venezuela were used for morphological examination and molecular analyses. Material of the new species is deposited in the collections of the Museo de Historia Natural Marina de Colombia (INV CRU) at the Institute of Marine and Coastal Research of Colombia, Santa Marta (INVEMAR), and the Forschungsinstitut und Naturmuseum Senckenberg, Frankfurt am Main (SMF), Germany. Specimens were sexed and measured by using a stereoscope with a micrometer. Measurements correspond to carapace length followed by carapace width.
DNA was extracted from the chelipeds or walking legs using the QIAGEN DNeasy®Kit following the protocol for animal tissue. A region of approximately 540 bp of the mitochondrial 16S rDNA gene was amplified with the primers
16Sar-L (5-CGCCTGTTTAACAAAAACAT-3) and 16Sbr-H (5-CCGGTTTGA ACTCAGATCATGT-3) (Palumbi et al., 1991). Double-stranded amplifications were performed in 25 μl volume reactions containing 5 μl of Taq buffer (5×), 2.5 μl of dNTP mix (8 mM, Promega), 1.2 μl of each primer (10μM), 2.5 μl of MgCl2 (25 mM), 0.2μl of GoTaq® Flexi DNA Taq Polymerase (Promega), 1 μl of DNA template, and 11.4 μl of ddH2O. Thermal cycling conditions consisted of an initial denaturation at 96°C for 3 min, followed by 30 cycles of 95°C for 1 min, 52°C for 1 min, and 72°C for 1 min. A final extension step at 72°C for 5 min followed the last cycle. PCR products were cleaned using ExoSAP-IT® (Affymetrix-USB) following the manufacturer’s protocol. Cleaned products were sequenced in both directions using the BigDye® Terminator v3.1 Cycle Sequencing Kit (Applied Biosystems) in 10 μl reactions as follows: 1 μl of PCR product was mixed with 4μl of ddH20, 3μl of sequencing buffer (5×), 1μl of primer and 1μl of BigDye ready-reaction mix. The mixture was subjected to thermal cycling conditions consisting of an initial denaturation step at 96°C for 1 min, followed by 25 cycles of 96°C for 10 s, 50°C for 5 s, and 60°C for 4 min. Cycle sequencing reactions were run on an ABI PRISM 3130xl Genetic Analyzer (Applied Biosystems). Two GenBank sequences were included in the data set: Pachycheles serratus (JF900732) and P. setimanus (Lockington, 1878) (JF900730), both from Bocas del Toro, Panamá. The later sequence caught our attention because P. setimanus is morphologically close to P. serratus (see below), but is restricted to the tropical East Pacific (Haig, 1960). Sequences were aligned using MAFFT v.7 (Katoh et al., 2002) with the L-Ins-i algorithm and default gap opening/extension penalties. Genetic distances within and between Pachycheles serratus and P. tuerkayi n. sp. were estimated using the Kimura-2-parameter model (K2P; Kimura, 1980) implemented in MEGA v.6.06 (Tamura et al., 2013).
DNA sequences obtained for this study were given GenBank accession numbers KY860741-KY860763.
RESULTS
Molecular results
The alignment of 23 partial sequences of the 16S rDNA gene was 535 bp long.
Average percent K2P distances within Pachycheles tuerkayi n. sp. (14 sequences in total) averaged at 0.17%, and within P. serratus (9 sequences in total) at 0.04%.
Distances between the two species averaged 6.8%. These distance estimations excluded the GenBank sequence labeled as P. serratus from Bocas del Toro, Panamá (JF900732), because it matched DNA sequences of the West Atlantic P. cristobalensis Gore, 1970 (A.H., unpublished data). The GenBank sequence
labeled as Pachycheles setimanus from Bocas del Toro (JF900730) matched sequences of Pachycheles tuerkayi n. sp. and, therefore, was included in our distance estimation.
Systematic account
Family PORCELLANIDAEHaworth, 1825 Pachycheles tuerkayi n. sp.
(figs. 1a, 2, 3)
Pachycheles serratus Haig, 1956 (part, pp. 8-9); Gore, 1970 (part, p. 962), 1982 (part, p. 9); Werding, 1977 (part, p. 194-195); Gore & Abele, 1976 (p. 20); Werding, 1978 (p. 219), 1982 (pp. 441-442);
Vargas & Cortés, 2006 (p. 485).
Material examined.— Holotype, male (5.1×5.4 mm), INV CRU 8408, Colombia, Magdalena, Santa Marta, El Morro, under boulders, 2-3 m, leg. B. Werding, 9 Sep 1974. Paratypes: 3 males (3.6 mm×3.8 mm, 4.0×4.3 mm, 4.8 mm×5.1 mm), 2 females (4.8 mm×5.5 mm, 4.2 mm× 4.7 mm), 2 ov. females (4.3 mm×5.0 mm, 5.2 mm×5.8 mm), INV CRU 8409, same data as holotype; 3 males (4.7×5.0 mm, 4.5×4.9 mm, 4.0×4.3 mm), 3 ov. females (5.0×5.8 mm, 4.8× 5.5 mm, 4.0×4.3 mm), SMF 50188, Colombia, Gulf of Urabá, Napú, under boulders, 2-4 m, leg.
B. Werding, 1977; 4 males (4.5×4.8 mm, 4.4×4.7 mm, 4.3×4.7 mm, 4.2×4.5 mm), 1 female (4.7×5.2 mm), 1 ov. females (4.8×5.2 mm), SMF 59189, Colombia, Magdalena, Santa Marta, under boulders, 0.5-2 m, leg. B. Werding, 1974.
Description.— Carapace somewhat broader than long in both sexes, dorsal sur- face smooth, metabranchial regions plicate, regions not marked. No epibranchial spine, epibranchial border crested. Front narrow, convex or slightly trilobate, scarcely produced, orbits deep, inner orbital angle rounded, outer orbital angle produced into a forwardly directed prominent tooth. Lateral walls with a trapezoid plate in anterior half and a large sub-quadrate plate frequently followed by a small fragment in posterior half.
First movable segment of antenna with a blunt conical tooth; second granulate and third cylindrical, smooth; flagellum two times as long as carapace. Basal segment of antennules forwardly directed, forming a rectangular, serrated lobe along the frontal margin.
Chelipeds thick, one distinctly larger, inner distal edge of merus produced into a large tuberculate lobe, upper surface with continuous transversal ridges;
carpus about as long as broad, surface with transversal scale like ridges and round granules, anterior margin armed with three large, irregular teeth, decreasing in size distally; dorsal surface covered distally with long, plumose setae which hide most of the frontal and distal borders. Posterior border slightly convex. Chelae extremely large, the bigger one exceeding by far the size of cephalothorax in large males (figs. 1a, 2). Distal border of chelae somewhat depressed at the level of the base of the pollex. Upper surface of chelae covered with round granules, most of the surface covered with thick setae, except on inner border and fingers. Fingers of
Fig. 1. a, Pachycheles tuerkayi n. sp. from Santa Marta, Colombia, large male, INV CRU 8409;
scale=4.5 mm. b, P. serratus (Benedict, 1901) from the Gulf of Morrosquillo, Colombia, large male. Scale=4.5 mm.
chelipeds slender, widely gaping in large specimens, and closing at entire length in smaller ones.
Walking legs slender, with scattered plumose setae more dense on carpus and propodus; dactylus slender, with three movable spines.
Males with pleopods; telson with seven plates.
Coloration.— The smooth carapace of Pachycheles tuerkayi n. sp. is brown, sometimes grayish, spotted with irregular light marks. The chelipeds are uniformly brown, darker in the distal parts of the fingers, whose tips are white. Setae on
Fig. 2. Pachycheles tuerkayi n. sp., male holotype, INV CRU8408, dorsal view. Scale=5.4 mm.
carpus and manus are beige. Walking legs are of the same colour as the carapace, a bit paler near articulations.
Ecology.— Pachycheles tuerkayi n. sp. lives in crevices between stones and other hard substrates in moderately exposed shallow water from intertidal areas to waters 6 m deep, often where there are fine sediments and some brackish water influence. It occurs with P. serratus in the same habitat in the Santa Marta region in Colombia.
Distribution.— Atlantic coast of Costa Rica, Panamá and Colombia, from Puerto Vargas (Costa Rica) to Islas del Rosario and Santa Marta (Colombia).
Etymology.— The new species is named after Michael Türkay, long-time friend and colleague.
Remarks.— Pachycheles tuerkayi n. sp. (figs. 1a, 2, 3) can be distinguished from P. serratus (figs. 1b, 4) by having (1) a carapace with smooth, shiny surface, (2) most of the cheliped’s dorsal surface densely covered with setae, and (3) the cheliped’s distal margin somewhat depressed on the level of the base of the pollex.
In P. serratus the surface of the carapace is coarser, the dorsal surface of the chelipeds bears no setae or only a few scattered ones, and the distal margin of the cheliped is not depressed. P. tuerkayi n. sp. and P. serratus belong to a
Fig. 3. Pachycheles tuerkayi n. sp., male holotype, INV CRU8408. a, carapace, frontal view;
b, carapace, lateral view. Scale=2.8 mm.
Fig. 4. Pachycheles serratus (Benedict, 1901), male, SMF 50196, chelipeds, dorsal view. Scale= 4.5 mm.
morphological group of Pachycheles species from the tropical Atlantic and eastern Pacific, characterized by having the carapace with scarce setae, and the carpus and manus of chelipeds covered with granules. This group is represented by P. chacei Haig, 1956 and P. cristobalensis in the Caribbean, by P. greeleyi (Rathbun, 1900) in Brazil, and by P. sahariensis Monod, 1933 in the eastern Atlantic. In the eastern Pacific the group is represented by P. calculosus Haig, 1960, P. setimanus and P. chacei (present on both sides of the Isthmus of Panamá). All species have a telson with 7 plates, except P. chacei, which has a 5-plated telson. P. tuerkayi n.
sp., P. serratus and P. setimanus have the presence of male pleopods in common.
Males in the other species in this Pachycheles group do not have pleopods.
DISCUSSION
Pachycheles tuerkayi n. sp. poses one more example of cryptic diversity within Porcellanidae. Other cases of species complexes in this family also comprise closely related species with overlapping distributions and ecologies (e.g., Hiller et al., 2006; Hiller & Werding, 2007). The new species and P. serratus diverge with average percent genetic distances (K2P=6.9%) larger than those estimated
between Pacific and Atlantic populations of the porcellanid Petrolisthes armatus (Gibbes, 1850) (K2P =1.5%), which are assumed to have been connected until the last stages of completion of the Isthmus of Panamá (Lessios, 2008). Pachy- cheles tuerkayi n. sp. and P. serratus probably diverged before the Isthmus fin- ished emerging. Following the descriptions and observations by other authors, we reconstructed the geographical distribution of these two species. Pachycheles ser- ratus was first described from Puerto Rico by Benedict (1901) as Pisosoma ser- rata. In the original description, this author does not mention or depict pubescence on the chelipeds (Benedict, 1901, pl. 3, fig. 7). Following Benedict’s description, Schmitt (1935) characterized the species’ chelipeds as “quite naked” and “more or less covered with bead-like rounded granules” and reported a range extension to St. Thomas and Cartagena, Colombia. Lira et al. (2007) described P. serratus from Venezuela as having sparse or lacking setation. Vargas & Cortés (2006) do not mention this character, but later revision of the specimens from Costa Rica revealed that they correspond to the new species (R. Vargas, personal communi- cation). P. serratus seems to be a common species with a northern distribution in Puerto Rico and the Virgin Islands and a coastal one in Panamá, Colombia and Venezuela. Pachycheles tuerkayi n. sp. seems to be the predominant species on the Caribbean coasts of Costa Rica, Panamá and Colombia, where it co-occurs with P. serratus, occupying the same habitats. More ecological observations are needed to establish how the two species share very similar or the same habitat.
ACKNOWLEDGEMENTS
We thank H. A. Lessios, L. Geyer, L. Rivera and A. Calderón (STRI) for support in the lab. We are grateful to S. Kalscheid for the drawings and to R. Vargas (Universidad de Costa Rica) for sharing useful observations of specimens from Costa Rica. We also thank E. Montoya, G. Borrero and M. Martelo (INVEMAR), and B. Trautwein (SMF) for their help with material curation and deposition.
This study was supported by a Smithsonian grant to A. H. and by the Centre of Excellence in Marine Sciences (CEMarin).
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First received 28 September 2016.
Final version accepted 19 April 2017.
